Red Blood Cell Aggregation Characterization: Using Norland Optical Adhesive Microfluidic Chips for a Reduction in Compliance

Abstract

The presence of red blood cell (RBC) aggregation is confirmed to be a rheological phenomenon implicating abnormal physiological conditions in vivo. However, there is presently no existing technology able to analyze, characterize and detect aggregation in vivo. The Laboratoire de Mécanique et d’Acoustique (LMA, UMR 7031), Centre National de la Recherche Scientifique (CNRS) at Aix-Marseille Universite (AMU) is developing a technology to measure blood aggregation in vivo using ultrasound backscattering techniques. In doing so it aims to allow disease prevention and disease recognition. The methodology developed at LMA is currently being compared to previous methodologies used to quantify RBC aggregation. Further study is needed to compare the methodologies used in LMA to microscopic imaging techniques, which are considered the gold standard in aggregation characterization. This thesis focuses on the development of a microfluidic device dedicated to the visualization of RBC aggregation. The device is capable of low compliance to ensure repeatability of the flow rate, with good optical clarity. The device’s co-flow properties and capabilities were tested and analyzed to ensure a proper comparison of methodologies could be conducted. Once completed, the incorporation of an ultrasound transducer to the setup, will be done in France to directly compare the methodologies developed by LMA and confirm the models derived by Franceschini et al. In order to develop the microfluidic chip, this thesis considers an overview of the methodology for characterizing RBC aggregation, the fabrication and compliant verification of a novel Norland Optical Adhesive microfluidic chip, and the shear rate calibration of the microfluidic device using Dextran 70 and Dextran 500. The NOA63 microfluidic device was calibrated to flow factors based on a shearing flow ratio of 25:1. The Norland Optical Adhesive microfluidic device had a much lower level of compliance in comparison to the gold standard of PDMS. The NOA63 device was found to be 51% less compliant than its counter part of PDMS. The device was calibrated to control shear rates from around 60s-1 to 0.01s-1. Multiple concentrations of Dextran 70 and Dextran 500 in human blood samples at 10% hematocrit were tested to characterize the shear rate in the blood layer. Aggregates were found to align themselves parallel to the flow and were observed to haven anisotropic shapes. All results from this thesis are being used to support the development of an ultrasound device capable of measuring blood aggregation in vivo.